What is chlamydia 

Chlamydia is an infection caused by the bacterium Chlamydia trachomatis. 

Chlamydia is a sexually transmitted infection (STI) and is one of the most common STIs worldwide. There are over 130 million new cases reported to the WHO (World Health Organisation) every year, although this is likely to be an underestimate as not all cases will be reported. It can be transmitted via vaginal, anal or oral sex. Chlamydia can also be transmitted from mother to child during childbirth. 

Treatment of chlamydia 

Chlamydia is a treatable infection - the usual treatment is oral antibiotic azithromycin (usually one tablet 1000mg, single dose) or doxycycline (usually 100mg, twice daily, given over the course of a week). Azithromycin is generally preferred as it is a single dose. In chlamydia cases where there is no complication, antibiotic therapy is 95% effective. It is important to take medications as instructed in order to clear the infection. Sexual activity is also advised against, for at least a week after the infection, in order to help avoid spreading to others. Re-infection however can occur from different sexual partners. 

If chlamydia is untreated 

Chlamydia can cause long-term complications with fertility if left untreated - particularly with those assigned females at birth. It can cause a condition known as pelvic inflammatory disease, which can inflame the female reproductive system (including cervix, uterus, and ovaries). This is often asymptomatic as well, so a person may not know there is a problem until they are trying to conceive. However, if there are symptoms, it can cause abdominal pain, pain during sex, and pain during urinating. Pelvic inflammatory disease can damage and scar the fallopian tubes and reduce the ability for an egg to move through them, into the uterus. It can also increase the risk of an ectopic pregnancy (where the egg is fertilised outside of the uterus, usually in the fallopian tubes). 

When to get tested 

If you notice any symptoms of chlamydia (in the section below) it is recommended that you are tested. 

If you do not have symptoms, there are instances where you should be tested as well: 

• If you have had sex with a new partner - especially without using a condom
• If you are a sexual partner of someone with a proven or suspected chlamydia infection 
• If you are under the age of 25 and have had a chlamydia infection within the last year
• If you are a woman seeking termination of pregnancy

Recommendations for screening (i.e. testing en masse) vary from country to country, but in the UK, the National Chlamydia Screening Programme recommends annual screening for all sexually active people aged 25 and under. It is common for chlamydia and gonorrhoea to co-occur, and so individuals should be tested for both. High-risk groups - those with multiple sexual partners or with a history of STIs - may be tested more frequently as they change partners.

However, if you do have any concerns about a sexual encounter (vaginal, anal or oral), it is always better to be safe and get tested. 

Symptoms of chlamydia

Most cases of chlamydia are asymptomatic, so the person infected would not necessarily know that they had the infection without testing, and therefore would not know if they have passed it on to any sexual partners. Asymptomatic infections make up 70-80% of cases in those assigned female at birth and around 40-50% of those assigned male at birth. For those assigned female at birth, cervicitis (inflammation of the cervix) is the most common result of chlamydia infections. In around 70% of cases, this is asymptomatic.^1,2

In only a minority of those assigned female at birth, there will be symptoms: a change in vaginal discharge; bleeding during sex; bleeding in between menstrual periods; pain in the abdominal area or a burning sensation when passing urine. 

Common symptoms in those assigned male at birth include discharge from the penis, pain in the testicles, discharge from the penis and a burning sensation when passing urine. The prostate gland can also become inflamed, known as prostatitis, which can also cause pain when urinating. 

Proctitis, which is inflammation around the rectum (anal) area, is usually seen in men who have sex with men (although anal sex occurs between heterosexual partners also). This is usually asymptomatic also but can cause pain and bleeding if there are symptoms. 

Chlamydia can also infect the eyes and cause conjunctivitis, which can be treated with azithromycin. In some parts of the world, where medical care is not available, people who have repeated eye infections with chlamydia can end up with a condition called trachoma, which can ultimately cause blindness. 

Testing in pregnancy 

Testing for chlamydia in the UK is not currently recommended. According to the UK National Screening Committee, this is because of insufficient evidence to show that a chlamydia infection will have any adverse outcomes on the pregnancy. They also reason that screening during pregnancy will not be beneficial for the baby or the pregnant woman and that treatment with antibiotics will not be of benefit. 

However, chlamydia can be transmitted from mother to child, and this is most likely to happen during childbirth. If a child does acquire chlamydia during childbirth, it can cause conjunctivitis or pneumonia - both of which are treatable, and usually do not cause any long term consequences for the child. 

Methods of testing 

There are different ways that samples can be taken in order to detect the presence of the Chlamydia trachomatis DNA. 

The first choice of swab is a vulvo-vaginal swab in those assigned females at birth as the bacterial DNA is more stable in these samples. The sample can be collected in a clinic by a health professional, but self-testing kits are also available. 

The second choice of sample is a first-catch urine (aka first-void urine) as this will contain more vaginal cells. This, as with a swab, can be taken by a health professional or with a self testing kit. Urine should be held in the bladder for 1 hour before the sample is taken, after which time the urine should be collected. 

In those assigned male at birth, first catch urine is the first choice of sample. This can be taken with a self-testing kit. A urethral swab can also be taken inserting it into the penis. 

Rectal samples (via swab) can also be taken in both men and women, either by a clinician or by self-testing. All HIV-positive MSM (men who have sex with men) should be tested with a rectal swab, whether or not they have symptoms of chlamydia. They should also be tested for another STD, lymphogranuloma venereum (LGV), as this can co-occur in this population. 

Challenges to testing for STIs

The largest global burden of STIs occurs in low and middle-income countries where there may be little or no availability of STI testing and treatment. Around the world, there are specific sects of the population that have the highest rates of STIs, including young people, mobile populations, sex workers, men who have sex with men, and transgender people. These people are also the ones who may not have access to adequate health services. 

There are also other barriers which deter people from accessing sexual health services even when they are available. These include any stigma of an STI, fear or embarrassment around an intimate examination, or inconvenience of going to get tested. Whilst these are very real problems that people have, it is important to prioritise health and not leave a disease untreated.

Informing partners 

If an individual is diagnosed, they should notify their sexual partners so that the partners can be tested themselves- both to limit the spread of the STI and to limit the consequences of leaving it untreated. It is however acknowledged that this is easier in principle, given the stigma around STIs. This can be especially true in cases of sex workers (or those who may not necessarily know their partners), or where there has been trauma or abuse. 

Summary 

Chlamydia is a curable STI with antibiotics, which have proven to be effective. People who are sexually active should be tested annually or if they become symptomatic. Those who are considered at a higher risk of acquiring an STI include people with multiple sexual partners, men who have sex with men, and those with a history of STIs. or these groups, more frequent testing is recommended. If left untreated, chlamydia can reduce fertility, especially in women. It is important to be tested for STIs, even in light of any stigma or fear, so that the disease can be picked up early and treated without causing long-term damage.